i have just begun testing an MTRON 32GB SATA SSD drive.
SATA means it can be plugged into any G5. Intel needs a SATA extension, until i find a drive tray adaptor.

SSD have very variable performance - they arent all fast. at all.
The SAMSUNG SSDs are only available with IDE interfaces. i have one - and the IDE interface is the limit to its performance.

MTRON drives are more expensive but much faster.
http://www.dvnation.com/nand-flash-ssd.html

Tests in my quad g5 show its almost as fast as scsi on most codecs - but can playback more than 10 dv layers at once (SCSI does about 7 ) . without any problems.